This invention relates to apparatus and method for detecting apnea, and more particularly to apparatus capable of detecting the cessation of airflow through the nostrils of a human infant.
Apnea is defined as the cessation of airflow generally for a period exceeding ten seconds. Apnea which lasts for a sufficient period can result in brain damage or even death. Apnea is believed to contribute in some instances to sudden infant death syndrome or so-called crib death. Because apnea is a life threatening condition, it is highly desirable to monitor those believed susceptible to apnea so that if breathing does cease steps can be taken to revive the affected individual. Infants suffering from respiratory distress syndrome or other diseases are particularly susceptible to the onset of apnea. Apnea in such infants may sometimes occur during bottle feeding.
Because of the potentially extreme seriousness of the condition, many apnea monitors have been developed to warn of the onset of the condition. Heretofore, several different parameters have been monitored to infer the onset of apnea. For example, chest or abdominal wall motion can be detected using strain gauge transducers or inductive plethysmographic coils. The onset of apnea is inferred if the chest wall or abdominal wall cease moving. Other techniques monitor the change in volume of the thoracic cavity or pressure changes within the lungs. Another indirect technique is the chemical analysis of the respiratory gases.
A more direct way of detecting obstructive apnea onset is to monitor airflow through the nostrils. The direct measurement of obstructive apnea by observing airflow is often a superior technique to impedance monitoring because in certain situations the other measurements can give false indications of obstructive apnea. For example, if chest and abdominal wall motions are monitored, it is possible for apnea to go undetected if there is an obstruction in the airway passages, for, in this case, the chest wall may still move without air flowing through the nostrils and into and out of the lungs. It will however pick up nonobstructive central apnea.
Several techniques are known for directly observing the onset of apnea by detecting airflow through the nostrils. These techniques include placing a mask over the subject's face and detecting apnea by means of a pneumotachygraph. Another technique is to place a thermistor in the airflow. In this case cessation of airflow will disrupt the normal temperature dependent changes in the resistance of the thermistor, allowing apnea to be detected. The known methods for monitoring the onset of apnea directly, that is, by monitoring airflow, are technically sophisticated and expensive to make and use which limits their universal applicability. The known apnea monitors also are not well suited for detecting apnea during the feeding of an infant. Clearly, a face mask would preclude feeding, and the placing of a thermistor near the nostrils of an infant might similarly disrupt attempts at feeding by annoyance to the infant and would also require electronic equipment to monitor resistance changes in the thermistor. Since it is known that apnea can occur during feeding, it is thus important to have an apnea monitor which is particularly well adapted for use during the feeding of infants.
It is therefore an object of this invention to provide apparatus and method for detecting apnea directly, that is, by detecting the cessation of airflow, in a simple, very inexpensive, easy to operate manner.
It is a further object of this invention to provide such an apnea monitor which is effective during the feeding of an infant.
Yet another object of this invention is an apnea monitor which is very sensitive and accurate.
A still further object is an apnea monitor capable of delivering oxygen or aerosol at feeding.
Other objects, features and advantages of this invention will be pointed out hereinafter.